Image forming apparatus including video data processing device

ABSTRACT

An image forming apparatus including a video data processing device in which a video controller that outputs video data using a reference clock and print data is improved. A radio frequency component that is not output as an actual image is removed from the video data so that it is possible to reduce emission of electromagnetic waves and to prevent image quality from deteriorating.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No.2007-14906, filed in the Korean Intellectual Property Office on Feb. 13,2007, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Aspects of the present invention relate generally to an image formingapparatus including a video data processing device for reducing emissionof electromagnetic waves (EMI) generated when video data is transmitted.

2. Related Art

An image forming apparatus, such as a laser printer and a multifunctionprinter, includes a video controller that converts print data into videodata and provides the video data to an exposure unit. An electrostaticlatent image is formed in a photosensitive drum by the exposure unit.Toner is supplied to transfer a developed toner image to a printablemedium, such as paper, supplied from a sheet cassette so as to print theimage onto the printable medium.

As shown in FIG. 1, the image forming apparatus includes a dataprocessing unit 40 connected to a personal computer (PC) 10, a scanner20, and/or a facsimile 30 to separately receive print data from the PC10, the scanner 20, and/or the facsimile 30, a video controller 50, andan exposure unit 60. The data processing unit 40 processes the printdata received from one of the PC 10, the scanner 20, and the facsimile30 so that a video controller 50 processes the print data.

As shown in FIG. 2, the video controller 50 generates video data basedon a reference clock and the print data received from the dataprocessing unit 40. The video controller 50 is formed of a chipset 50 ato transmit the generated video data to the exposure unit 60 outside thechipset 50 a. The exposure unit 60 provides the video data to a laserdiode 63 through a signal cable 62 of a printed circuit board (PCB) 61.The video data turns on or off the laser diode 63 and controls theoperation of the laser diode 63 so as to constitute a part of theexposure unit 60 to which the toner is adhered and a part to which thetoner is not adhered so as to correspond to a printed output image. Analgorithm for converting data is programmed into the video controller50.

The video controller 50 changes the duty ratio of the video data usingthe programmed algorithm to improve image quality and outputs the videodata. The video data, as shown in FIG. 3B, generates a pulse columnhaving a frequency different from the frequency of the reference clock,shown in FIG. 3A, provided to the video controller 50 and having a dutyratio different from the duty ratio of the reference clock provided tothe video controller 50.

Not all of the electrostatic latent images formed in the photosensitivedrum are output as actual images. Although an electrostatic latent imageis formed in the photosensitive drum, if the amount of the toner isinsufficient to be adhered to the electrostatic latent image, the tonerimage is not formed, and no image is formed on the printable medium.

As shown in FIGS. 3A-3D, although the frequency is not changed by thevideo controller 50, since the duty ratio changes, the video data hasmore radio frequency components than the reference clock, as shown inFIG. 3B. For example, if the video data includes a pulse vd1 having avery small width, a switching operation of being turned on or off is notperformed due to limitations on the recognition of the laser diode 63.In addition, although the laser diode 63 performs the switchingoperation and virtual dots are output, actual dots are not formed on theprintable medium.

Furthermore, since the video data is transmitted from a main board inwhich the video controller 50 is mounted to the laser diode 63 of theexposure unit 60 that emits the laser beam through the signal cable, thetransmission channel is long so that, when a complicated picture isprinted, electromagnetic interference (EMI) is generated by the radiofrequency component of the video data.

As described above, since the radio frequency component included in thevideo data causes emission of electromagnetic interference during signaltransmission, remedial measures are required. In addition, since theradio frequency component does not contribute significantly to imagequality, such a radio frequency component can be removed withoutcompromising the quality of an actually output image.

SUMMARY OF THE INVENTION

Aspects of the present invention provide an image forming apparatusincluding a video data processing device by which a radio frequencycomponent that is included in video data and is not output as an actualimage is removed so that it is possible to reduce electromagneticinterference (EMI) generated in the process of transmitting the videodata and to prevent image quality from deteriorating.

According to an aspect of the present invention, an image formingapparatus is provided. The image forming apparatus includes a dataprocessor to generate video data, a video controller to remove a radiofrequency component included in the video data during generation of thevideo data so as to mitigate emission of electromagnetic interference,and to provide the video data to a light source of an exposure unit tobe printed onto a printable medium.

According to another aspect of the present invention, the videocontroller includes a quasi-video data generator to receive a referenceclock and print data and to generate quasi-video data based on thereference clock and the print data; and a filter to remove a pulses inthe quasi-video data based on a magnitude of a width of the pulses.

According to another aspect of the present invention, the videocontroller further includes a storage unit to store information relatedto a reference pulse width.

According to another aspect of the present invention, the image formingapparatus further includes a data processing unit to provide the printdata to the quasi-video data generator.

According to another aspect of the present invention, the dataprocessing unit processes the print data received from one of a personalcomputer, a scanner, and a facsimile.

According to another aspect of the present invention, the referencepulse width is set to be in a range recognized by the light source ofthe exposure unit.

According to another aspect of the present invention, the light sourceis a laser diode.

According to another aspect of the present invention, the video dataincludes a pulse column having a frequency the same as a frequency ofthe reference clock and having a pulse width is different from the pulsewidth of the reference clock.

According to another aspect of the present invention, an image formingapparatus comprising a video data processing device is provided. Thevideo data processing device includes a data processing unit to processprint data received from one of a personal computer, a scanner, and afacsimile machine; a quasi-video data generator to generate quasi-videodata based on a reference clock and the print data received from thedata processing unit; a storage unit to store information related to areference pulse width, a filter to remove pulses of the quasi-video datahaving a pulse width smaller than the reference pulse width and tooutput the processed quasi-video data as video data, and a light sourceto receive the video data and to output light so as to generate anelectrostatic latent image to be printed onto a printable medium.

According to another aspect of the present invention, the quasi-videodata generator, the storage unit, and the filter are provided in a mainboard and the exposure unit receives the video data through a signalcable connected to the main board.

According to another aspect of the present invention, the video data isgenerated as a pulse column having a frequency the same as a frequencyof the reference clock and having a pulse width different from the pulsewidth of the reference clock.

According to another aspect of the present invention, the informationrelated to the reference pulse width stored in the storage unit is basedon a range of recognition of the light source.

According to another aspect of the present invention, the light sourceis a laser diode that receives the video data through the signal cableso as to be turned on or off and to emit a laser beam.

Additional aspects and/or advantages of the invention will be set forthin part in the description which follows and, in part, will be obviousfrom the description, or may be learned by practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the invention will becomeapparent and more readily appreciated from the following description ofthe embodiments, taken in conjunction with the accompanying drawings ofwhich:

FIG. 1 is a block diagram of a conventional image forming apparatus;

FIG. 2 is a block diagram of a conventional video controller;

FIGS. 3A-3D illustrate output timing diagrams of an output image of theconventional video controller;

FIG. 4 is a block diagram of an improved video controller applied to animage forming apparatus according to an example embodiment of thepresent invention; and

FIGS. 5A-5E illustrate output timing diagrams of an output image of avideo controller according to an example embodiment the presentinvention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the present embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to the like elementsthroughout. The embodiments are described below in order to explain thepresent invention by referring to the figures.

FIG. 4 is a block diagram of an improved video data processing deviceapplied to the image forming apparatus according to an exampleembodiment of the present invention. A video controller 150 includes aquasi-video data generator 151, a filter 152, and a storage unit 153. Asshown in FIG. 4, the video controller 150 receives a reference clock andprint data, generates video data after removing a radio frequencycomponent included in the video data, and outputs the generated videodata to an exposure unit 60 outside a chipset 150 a, which is similar tothe conventional video controller. Such a video controller 150 may beformed by a the chipset 150 a installed to transmit the generated videodata to the exposure unit 60 outside the chipset 150 a. The exposureunit 60 provides the video data to a laser diode 63 through a signalcable 62 of a printed circuit board (PCB) 61.

The video data received from the video controller 150 is used to controlthe operation of the laser diode 63, i.e., turns on/off the laser diode63, so as to constitute a part of the exposure unit 60 to which thetoner is adhered and a part to which the toner is not adhered so as tocorrespond to a printed output image. An algorithm for converting datais included in the video controller 150.

Referring back to FIG. 4, the quasi-video data generator 151 receivesthe reference clock and the print data from the data processing unit 40,generates quasi-video data using the built-in algorithm, and providesthe quasi-video data to the filter 152. The algorithm to improve imagequality makes a frequency of the quasi-video data the same the frequencyof the reference clock and changes a duty ratio of the quasi-video data.The quasi-video data is obtained as a result of processing the printdata using the algorithm.

Turning now to FIGS. 5A-5E, timing diagrams of an output image areshown. The quasi-video data output from the quasi-video data generator151, as shown in FIG. 5B, may include a pulse vd1 having a very smallwidth. The very narrow pulse vd1 is the radio frequency component. Theradio frequency component may not be recognized by the laser diode 63,and so the switching operation of being turned on or off is notperformed. Even if the laser diode 63 performs the switching operation,virtual dots are output as shown in FIG. 5D and actual output dots arenot formed on a printable medium, as shown in FIG. 5E. The radiofrequency component is thus an unnecessary component of the print data.As a result, removing the radio frequency component will not affect theimage quality.

The filter 152 removes the very narrow pulse vd1 that is the radiofrequency component included in the quasi-video data and transmits thevideo data from which the radio frequency component is removed to theexposure unit 60 outside the chipset 150 a. The filter 152 determineswhether a pulse is to be removed in accordance with the magnitude of thepulse width among the pulses of the video data. The filter 152 receivesinformation from the storage unit 153 related to a reference pulse widthused to determine whether to remove the pulse. The reference pulse widthis set to be in a range where the laser diode 63, as shown in, forexample, FIG. 1, can recognize the operation of being turned on or off.

The filter 152 maintains a pulse state if the pulse width is not smallerthan the reference pulse width, and removes the very narrow pulse vd1that is the radio frequency component to output the video data when thepulse width is smaller than the reference pulse width.

As shown in FIG. 5, the video data from which the radio frequencycomponent is removed by the filter 152 is transmitted to the laser diode63 through the signal cable 62 of the exposure unit 60. As describedabove, in the process of transmitting the video data, electromagneticinterference (EMI) caused by the radio frequency component issignificantly reduced.

Hereinafter, the operation of the video processing device of the imageforming apparatus according to an embodiment of the present inventionwill be described. The data processing unit 40 separately receives printdata from a personal computer (PC) 10, a scanner 20, and/or a facsimile30, processes the received print data so as to be processed by the videocontroller 150, and provides the processed print data to the videocontroller 150. The quasi-video data generator 151 generates thequasi-video data based on the reference clock and the print datareceived from the data processing unit 40 and provides the quasi-videodata to the filter 152.

The filter 152 receives the information related to the reference pulsewidth from the storage unit 153 to output the video data with a pulsemaintained when a pulse width of the quasi-video data is not smallerthan the reference pulse width and to output the video data from whichvery narrow pulses making up the radio frequency component is removedwhen a pulse width of the quasi-video data is smaller than the referencepulse width. The filter 152 transmits the video data from which theradio frequency component is removed to the exposure unit 60 outside thechipset 150 a. The exposure unit 60 provides the video data from whichthe radio frequency component is removed to the laser diode 63 throughthe signal cable 62 of the PCB 61.

As described above, according to aspects of the present invention, thevideo controller removes the radio frequency component included in thevideo data to transmit the video data to the exposure unit so that it ispossible to reduce the emission of the electromagnetic waves generatedduring the transmission of the video data without deteriorating theimage quality of the printed output.

Although a few embodiments of the present invention have been shown anddescribed, it would be appreciated by those skilled in the art thatchanges may be made in this embodiment without departing from theprinciples and spirit of the invention, the scope of which is defined inthe claims and their equivalents.

1. An image forming apparatus comprising: a data processor to generatevideo data; and a video controller to remove a radio frequency componentincluded in the video data during generation of the video data so as tomitigate emission of electromagnetic interference, and to provide thevideo data to a light source of an exposure unit to be printed onto aprintable medium.
 2. The image forming apparatus as claimed in claim 1,wherein the video controller comprises: a quasi-video data generator toreceive a reference clock and print data and to generate quasi-videodata based on the reference clock and the print data; and a filter toremove pulses in the quasi-video data based on a magnitude of a width ofthe pulses.
 3. The image forming apparatus as claimed in claim 2,wherein the video controller further comprises a storage unit to storeinformation related to a reference pulse width.
 4. The image formingapparatus as claimed in claim 2, further comprising a data processingunit to provide the print data to the quasi-video data generator.
 5. Theimage forming apparatus as claimed in claim 4, wherein the dataprocessing unit processes the print data received from one of a personalcomputer, a scanner, and a facsimile.
 6. The image forming apparatus asclaimed in claim 3, wherein the reference pulse width is set in a rangerecognized by the light source of the exposure unit.
 7. The imageforming apparatus as claimed in claim 6, wherein the light source is alaser diode.
 8. The image forming apparatus as claimed in claim 1,wherein the video data comprises a pulse column having a frequencyidentical to a frequency of the reference clock and having a pulse widthdifferent from a pulse width of the reference clock.
 9. An image formingapparatus comprising a video data processing device, the image formingapparatus comprising: a data processing unit to process print datareceived from one of a personal computer, a scanner, and a facsimilemachine; a quasi-video data generator to generate quasi-video data basedon a reference clock and the print data received from the dataprocessing unit; a storage unit to store information related to areference pulse width; a filter to remove pulses of the quasi-video datahaving a pulse width smaller than the reference pulse width and tooutput the processed quasi-video data as video data; and a light sourceto receive the video data and to output light so as to generate anelectrostatic latent image to be printed onto a printable medium. 10.The image forming apparatus as claimed in claim 9, wherein thequasi-video data generator, the storage unit, and the filter areprovided in a main board, and the exposure unit receives the video datathrough a signal cable connected to the main board.
 11. The imageforming apparatus as claimed in claim 9, wherein the video data isgenerated as a pulse column having a frequency the same as the frequencyof the reference clock and having a pulse width different from the pulsewidth of the reference clock.
 12. The image forming apparatus as claimedin claim 9, wherein the information related to the reference pulse widthstored in the storage unit is set is based on a range of recognition ofthe light source.
 13. The image forming apparatus as claimed in claim 9,wherein the light source is a laser diode that receives the video datavia a signal cable so as to emit a laser beam.
 14. A method ofmitigating electromagnetic interference generated by an image formingapparatus, the method comprising: receiving quasi-video datacorresponding to an image to be formed onto a printable medium; removingradio frequency components of the quasi-video data having a pulse widthsmaller than a pulse width of a reference pulse width so as to generatevideo data and mitigate emission of electromagnetic interference; andforming the image onto the printable medium corresponding to the videodata.
 15. The method of claim 14, wherein a width of the reference pulseis set in a range recognized by a light source used to form the imageonto the printable medium.
 16. The method of claim 14, furthercomprising: generating the quasi-video data based on a reference clockand print data corresponding to the image to be formed onto theprintable medium.
 17. The method of claim 16, wherein the video datacomprises a pulse column having a frequency identical to a frequency ofa reference clock used to generate the quasi-video data and having apulse width different from a pulse width of the reference clock.